Means for compensating speedometers and similar devices for temperature variations.



\ E. M. THOMPSON. MEANS FOR COMPENSATING SPEEDOMETERS AND SIMILARDEVICES FOR TEMPERATURE VARIATIONS. AIPLICATION FILED NOV. 2, I910.

Si. M. THOMPSON.

MEANS FOR COMPENSATING SPEEDOMETERS AND'SIMILAR DEVLQES FORTEMPERATUREVARIATIONS.

APPLICATION FILED Nov. 2. mo.

1,134,649. Patented Apr. 6, 191-5,

2 SHEETS-SHEET zl' menses.

sin, have made a certain new and us H inn sna nis meme entice.

EDWARD M. THOMPSON, OF BEL-O11, W'ISCQNSIN, ASSIGNOR TO ST'ElVART-WAL.AR

SPEEDOMETEB. CORPORATION, A CORPORATION OF VIRGINIA MEANS FORCOMPENSATING SPEEXBQMETEBS AND SIMILAR DEVICES FOR TEMPERATUREVABEATIQNS.

Patented Apr. 6, 1915.

Application filed Novemli'ez; 2, 1910. Serial No. 590,275.

To all whom it may concern:

Be it known that I, EDWARD M. Teenssox, a citizen of the United States,residing at Beloit, county of Rock, State of llliscon l in vention' inMeans for Compensating Speedometeis and Similar Devices for'llempetmture Variations, of which. the following is a, specification.

The invention relates generally to devices of the class known astachometers, and, ps1.

ticula'rly to speed indlcatimg; devices such for instance, as areemployed in connection with automobiles to indicate-their speed. of

travel. I v

The object of the invention is to provide means which are simple andeliicient for antomatically compensating instruments of the 'classreferred to. for temperature variations,

whereby to automatically secure accuracy of speed. indications atdifferent atmospheric temperatures.

" Other ob ects of the invention will appear 1 more fully hereinafter.

o pensatmg means.

The invention. consists substantially of the construction, combination,location and relative. arrangement of ports, all as will he more fullyhereiuaftei" set forth, as shown in the sccompanving drawings. andfinally pointed out in the ai'ipended claii'us.

Referring to the accoinpan ing' dmwings and to the various views and toiet-once signs appearing thereon, Figure 'l is a view in partial verticalcentral section of a form 'oiinagnetic speed indicating}; instrumentshowing the application thereto 03? means for compensating for pherictemperatures.

variations in atmos- Fig. 2 l8 a top plan View of a portion of theinstrument showing the manner of applving the automatic com- Fig. 3 is aview in side elevation of the constiuction shown in Fig. 2, and-partlyin section on the line 3; 3, Fig. 2; looking in the direction of thearrows. Fig. 4 is an enlarged biOkGIl detail view in top plan, partsbroken out, showing the an ranaement of the automatic coi'npensatingmezins. Fig. 5 is a broken view inelevation, showing one form of scalearrann ctzwnt cuinloyed in connection with instruuu of the classreferred to.

The same part is reference characten wherever throughout the severalviews.

designated by the same it occurs hes heen the custom to adjust the partsto give accurate readings at an average mean temperatune. For ordinarypurposcs oi' use of the instruments this is usually sul'licient sincethe variations in indications dueto changes in atmospheric temperatureunder the conditions of use of the instruments, particularly asautomobile speed indicator-sis small. That this is true will be evidentwhen it is considered that, otdinai-ily, the automobile is notextensively used in extremely. cold Xv other, and seldom in climatesWhere subjected to excessively high temperatures. It may sometimes.however he desirable to make compensating adjustment for even the smallvai'iations of the indications of instruments of the class referred to,due to varying atmospheric tempezature conditions under which theinstrument is used. and wheii ehy an accurate and correct inclication isgiven at all temperatl'lres. 'Theao coinplishment of this result isamong the special olojects'and purposes of my invention. I I

in instruments of this class the desired speed indications are made bymeans of an associated scale and nointor or hand...one of these Da'itScoins; fixed and the other an ranged to he i-otatively disnlacedptoiuutionally to the speed to he indicated. The rots tii'elv dislacealizlc memliier usually held yieldinnl in an inn? l =01 "nei'oposition and is iotativelv d' 'rlaccd position and against the action ofa hair or other spring. placii'igg the movahle member of the scale andpointer mechanism may he varied throughout a Wide range and variouscondevice is relatively disnlaced o means of a rotating: magnetic field.it is to be understood that my inventimi as defined 1n {the not to belimited or restricted to cola? "too of instrument. v I in t inaqnctic tme of instrumentthe movalle nieml' ez? of the scale andTnointer claimsdevice 1151mm associated with a disltcup or other convenient form ofdevice or memheir arranged "Withmthe influence of a PO" "from suchinitial The means to? rotatively dis elen'ient of the scale-and-pointer'.tating magnetic field, and of such material as to be influenced androtatively displaced against the action of the hair spring by themagnetic drag of the rotating magnetic field.

Various arrangements of means for producing the rotating magnetic fieldare em bodied in instrm'nents now on the market, and while I have shownand will describe one form of means for accomplishing the desiredresults, myinvention, as defined in the claims is not to be limited orrestricted to this particular arrangement.

In carrying out my invention I propose to employ a thermostatic or otherdevice capableof being influenced by variations in atmospherictemperatures and having suitable connection to the hair or other springemployed to yieldingly resist the rotative action imposed. by therotating magnetic field upon the movable part of the scale-andpointcrdev'ce, in such manner as to vary the effective tension of said springby and in proper proportional relation to the variations in atmospherictemperature.

Many specifically different constructions and arr-al'igements may bedevised for carrying this arrangement into practical operation. vl/hile,therefore, I have shown, and will now describe, one form of meansforaccomplishing the desired objects, my invention, as defined in theclaims, is not to be limited or restricted in their broadest scope tothe particular construction herein set forth.

In the drawingsA, designates a casing in which is mounted to rotate amagnet B, rotation being imparted to the magnet by suitable connectionwith the shaft or other part the speed of which is to be indicated. 40

Cooperating with the magnet is a magnetic mass O, for the purpose ofconcentrating the magnetic field. In the particular form shown, towhich, however, my invention, as

defined in the claims, is not to be limited,

the mass C, is stationary, and is carried in an auxiliary case F,adapted to be mounted in the main case A,oi' the instrument. In terposedbetween the magnet B, and mass C, or in such relation thereto as to becut by the lines of force of the magnetic field maintained between saidmagnet and mass, is a member D, which is mounted on a spindle E,journaled in suitable hearings in the auxiliary case F. In this instancethe member D constitutes the rotative or movable part of thescale-and-pointer part of the instru- 'ment, and carries the scale G,see Fig. 5, with which cooperates the pointer H. The scale'member D, isnormally held in an ini- -tial or Zero position by means of the hairspring J, which is connected at one end to spindle E, and is so arrangedwith reference thereto as to yieldingly resist the rotative movements ofthe spindle.

The partsso-fardescribed, as above indi mostatic device, that is, adevice W'llh cated,'may be of the usual or any well known type andconstruction, and in the specific details of structure and arrangementthereof formno part of my present invention, and may, therefore, bechanged and varied tl'iroughout a wide range.

Reference numeral 10, designates a. thersensitive to heat variations,and which, in the particular construction shown comprises two strips ll,12, of metal possessing di1"'- ferent coefficients of expansion orcontraction under the influence of heat, such, for instance as brass andsteel. In the form shown these metal strips 11, 12, are secured togetherin the form of a compound split ring. One end of this split ring issecured to a fixed part the auxiliary case if, as, for instance, bymeans of the screw 13. The other end of the split thermostatic ring isfree and carries a pin 1-1, upon which is pivoted, at one end, a leverl.This lwer is pivoted upon a fulcrum pin 16, carried in an arm-orextension 17, of a fixed part of the case. At its free end lever 15 isforked, as indicated at 18, to straddle a pin 19, carried in orconnected to the free endof the hair spring J. The pin 19 is alsocarried by or connected to a. rocking or swinging arm 20, pivoted upon afixed part of the etationary auxiliary case F. The arm 20, it will beobserved serves as a rocking keeper for the pin 19, which is connectedto the end of the spring permits the pin 19, to move in the arc of'acircle about the pivot of arm 20, while lever 15 rocks about its fulcrumpin 16.

While I have shown and described in de= tail a specific structureoftemperature compensating device and connections, it will be understoodthat my invention, as defined in the claims, is not to be limited orrestricted to that specific structure, the essential features being theprovision of thermostatic devices having connection with the hair orother spring which yieldingly resists the rotative movements imparted tothe movable member of the scale-and-pointer devices of a speedindicator, the connections being such as to vary the effective tensionof the spring in substantially exact relation and proportion tovariations in atmospheric temperature, thereby correspondingly varyingthe yielding resistance to the rotative movemerit of the movablemember-.01 the scale and pointer devices.

The operation of the-specific structure shown is very simple. Thevariations in atmospheric temperature effect the thermostatic ring,causing movements of its free end, thereby rocking lever l5, about itsfulcrum 16, hence, through the engagement of the slotted end of saidlever with the pin 19, causing said pin to move in a path determined bythe swinging arm 20,

J. The slot 18. in the lever 15,

which. carries it, thereby correspondingly varying'the effective tensionof the spring J Many variations and changes in the details of structureand arrangement wouldreadily occur to persons skilled in the art withoutdeparture from the spirit and scope of my invention as defined in theclaims.

Having now set forth the objects and nature of my inventionv and oneform of construction embodying the principles thereof, and havingexplained such construction and its mode of operation, what I claim asnew and useful and of .my own invention,

and desire to secure by Letters Patent is,-

1. In a speed indicating device, a scale member, a pointer associatedtherewith, a spindle connected to one'of-these parts, a spring connectedat one end to said spindle and carrying a pin at its other end, apivotally mounted keeper] arm for said pin, a

pivoted lever engaging said pin, a thermostatic device connected tosaidlever for rocking the'same, and means operated by the shaft, the speedof which is to be indicated, for rotatively 'moving said spindleagainst'the action of. said spring.

2. Inv a'speed indicating device, 'a scale member, a pointer associatedtherewith, a spindle connected to one of these parts, a

. spring connected atone end to saidspindle and carrying a-pin .at itsother end, a piv otally mounted lever having loose connection at one endwith said pin, a thermostatic device connected to the other end' of saidlever for rocking the same, and'means operated by the shaft or part, thespeed of- EDWARD M. THOMPSON.

Witnesses:

M. R. BURNS, V. A. Rosa.

